1. Field of the Invention
The present invention relates to receiver protectors and, more particularly, to receiver protectors for radar systems where high power transmit RF pulses and relatively low power receive RF pulses propagate in a common waveguide type transmission line.
2. Description of Related Art
Receiver protectors for present state of the art high power radar systems are generally known and in some systems utilize radioactive tritium or promethium-147 materials to generate seed electrons to initiate gas breakdown. A continuous supply of xcex2 emission, i.e. electrons, is provided by such sources and normally have a useful life of more than 30 years, particularly in tritium primed devices. Radioactive sources do not require any external power to generate seeding electrons and, therefore, are useful in passive receiver protectors. However, radioactive sources provide safety hazards and are expensive to store, dispose of, and repair.
Solid state receiver protectors using high power silicon PIN diodes have also been designed as an alternative to radioactive primed gas plasma stages. However, the peak and average power handling capabilities of these devices are generally limited to 3-5 kilowatts peak and 100-200 watts average, at X-band, due to the need for fast recovery time and low insertion loss. High power handling capability, up to megawatt levels, passive operation, fast recovery times, low insertion loss, and low spike/flat leakages are thus advantages of gas plasma receiver protectors.
In addition, use of quartz gas envelopes in receiver protectors have extended the lifetime of these devices beyond 30 years for many applications. In some designs, a solid state receiver protector is also used for continuous operation which is preceded by a glass plasma stage as an overload protector in order to achieve long lifetimes.
With respect to non-radioactive gas plasma stages, prior designs of receiver protectors have included a DC keep-alive voltage in the priming source. However, this has the disadvantage of requiring a relatively high voltage power source on the order of 400 VDC while having a lifetime of only a few hundred hours.
RF primed gas stages are also known in the art, but have been relatively expensive to fabricate. Generating priming electrons by field emission using a cathode within an array of fine diamond tips which act as field emitting diodes is also a known concept but has the disadvantage of suffering damage during high power RF transmission through the device, thereby limiting its useful lifetime.
Also, while the concept of generating high energy photons by the use of high energy short duration lasers is generally known, they are generally undesirable for radar receiver protector applications.
Accordingly, it is an object of the present invention to provide an improvement in receiver protector apparatus for radar systems.
It is a further object of the invention to provide a non-radioactive gas plasma receiver protector for radar systems.
And it is a further object of the invention to provide a photon primed non-radioactive gas plasma receiver protector for radar systems.
These and other objects of the invention are achieved by a receiver protector for a radar system including a photon source as a priming device for a gas plasma type receiver protector, and where the priming device comprises a light source in the form of a miniature high intensity blue light emitting diode (LED) ranging in wavelength from 470 nm to 490 nm or an ultra-violet LED or miniature lamp or laser diode ranging in wavelength from 260 nm to 470 nm.
In the broadest aspect of the invention, it is directed to a photon primed non-radioactive gas plasma receiver protector for radar systems, comprising: a section of microwave transmission line coupled to radar receiver apparatus and including an input port and an output port; a first and a second RF reflection stage located between the input port and the output port of the section of transmission line for reflecting RF energy incident at the input port while propagating an attenuated portion of the RF energy to the output port; said first reflection stage including a discharge gap and at least one container including an ionizable gas located adjacent the discharge gap; said second reflection stage being positioned relative to the first reflection stage so as to reflect maximum RF energy back to the discharge gap to produce ionization of the gas in the container upon incidence of RF energy at the input port; and, at least one photon source in the first reflection stage for emitting photons ranging in wavelength from about 260 nm to about 490 nm and operating as a primer so as to generate seed electrons which initiate ionization of the gas in the container in response to incident RF energy at the input port.
Further scope of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood, however, that the detailed description and specific examples, while disclosing the preferred embodiments of the invention, they are provided by way of illustration only, since various changes and modifications coming within the spirit and scope of the invention will become apparent to those skilled in the art from the detailed description.